(1) Field of the Invention
The present invention relates generally to a system for automatically shutting down cooking appliances and/or associated equipment in accordance with NFDA recommended standards in the event of a fire, and in particular to a fail-safe system of this type that will also shut down in the event of a failure in the system, and which will continue to indicate a failure until corrections are made by authorized personnel.
(2) Description of the Prior Art
Commercial kitchens and related facilities having a plurality of cooking appliances are normally equipped with a fire extinguishing mechanism that is automatically activated in the event of a fire, such as a grease fire, at one of the appliances. The extinguishing mechanism is usually comprised of a source of an extinguishing chemical that is connected via a piping network to discharge ports that are directed toward the cooking surfaces of the appliance. A discharge valve is used to control the flow of chemicals from the source. The discharge valve is adapted to be opened when an associated mechanism detects a fire.
For example, a spring-loaded discharge valve may be held in a closed position by a taut cable, which includes one or more fusable heat links positioned above the cooking appliances. When one of the links is melted by the heat from a cooking fire, the cable is released, opening the discharge valve, and discharging fire extinguishing chemicals onto the surfaces of the cooking appliances to extinguish the fire.
An effective, complaint fire extinguishing system must also include means to disconnect the cooking appliances from the energy source when a fire is detected. Otherwise, the fire-extinguishing chemical will be exhausted, and the fire may continue or restart due to the continuing supply of energy, i.e., electricity or gas. In the case of an electrical appliance, the appliance is de-energized by opening the electrical circuit to the appliance. In the case of an gas fueled appliance, the appliance is de-energized by shutting off the gas supply, e.g., by closing a valve, such as a solenoid actuated valve.
An effective system should also include an alarm to alert others to the existence of the fire. This alarm can be activated at the time the chemical is discharged, and continues to emit a signal, e.g., a sound and/or a light signal, until manually disconnected. The inclusion of a signal mechanism is mandated by NFPA-17A of the National Fire Protection Codes for xe2x80x9cWet Chemical Extinguishing Systemsxe2x80x9d used for restaurant canopy hoods. NFPA-17A states:
xe2x80x9cA signal shall be provided to show that the system has operated, that personnel response is needed, and that the system is in need of recharge. The extinguishing system shall be connected to the fire alarm system, if provided, in accordance with the requirements of NFPA 72, National Fire Alarm Codes, so that the actuation of the extinguishing system will sound the fire alarm as well as provide the function of the extinguishing system.xe2x80x9d
Various fire extinguishing systems for use with restaurant cooking appliances have been proposed in the prior art. The following patents are representative of prior art systems:
Despite considerable efforts, there is still a need for a system for effectively de-energizing a plurality of cooking appliances and other restaurant equipment, as required, in the event of a fire, while emitting a signal as required by NFPA-17A. In particular, a system of this type is needed that will not only de-energize appliances in the event of a fire, but which will de-energize appliances in the event of a detected failure in the microswitch or other circuit component. Therefore, the user will not be falsely assured that a functional system is being used to monitor conditions when, in fact, the system is not functioning.
A system of this type should also be designed so that the alarm cannot be fully deactivated until the system has been recharged after a discharge of chemical, or has been repaired after a malfunction has been detected. For example, if the alarm system includes both a sound and light emitting components, the operator should be prevented from disconnected both components until the system has be recharged or repaired by authorized and skilled personnel.
The present invention is directed to a shutdown or control system for de-energizing kitchen appliances in the event of a fire. The system is used in conjunction with a fire extinguishing system comprised of a source of fire extinguishing chemical or other material, a release mechanism for releasing the fire extinguishing material in the event of a fire.
Basically, the shutdown system is comprised of a normally closed switch, positioned to be opened when the fire extinguishing system is activated, a plurality of relays that change state when the switch is opened, the relays being capable of de-energizing appliances, and an alarm mechanism that includes an audible component that can be deactivated by an operator, and a visual component that can only be deactivated by repair and recharging of the fire extinguishing system.
Preferably, the normally closed switch is positioned in the path of a component of the fire extinguishing system that moves from a ready position to a released position when a fire is detected, so that the component engages the switch to move the switch from a closed state to an open state. For example, the switch can be a microswitch that is positioned adjacent a component of a fire extinguisher discharge valve control mechanism that moves from a restrained position to a released position when a fire is detected, so that the component engages the microswitch when at the released position.
More specifically, the fire extinguishing system may be comprised of a control mechanism that includes a pivotal member moveable between first and second positions, with the pivotal member being urged toward the second position by a spring, and held in the first position by a cable that includes a heat fusable link. In the event of a fire, the heat fusable link is severed by the heat from the fire, releasing the cable and allowing the pivotal member to move under the influence of the spring to the second position.
A microswitch is positioned at the second position in the path of the pivotal member, so that a component of the pivotal member engages the microswitch to move the switch from the closed state to the open state. The pivotal member also engages a release member, such as a valve, to release fire extinguishing chemicals from a supply source, such as a pressurized tank.
The microswitch is in a primary circuit with a plurality of relays that are in secondary circuits with different appliance controllers, e.g., switches or valves. The circuits are designed so that the circuits to the appliances are in a closed or completed state when the microswitch is closed. These circuits may be designed with the relays in an open state or a closed state. Thus, for purposes of description, when the appliances are energized, the relays will be described as being in the energized state, and in the deenergized state when the appliances are deenergized.
The microswitch is also in a circuit with an audible alarm, such as a horn, and a visual alarm, such as a strobe light. The audible and visual alarms are in a deenergized state when the microswitch is closed, and are moved to the energized state when the microswitch is opened. The horn is also in a circuit with a switch that can be used to deactivate the horn.
During the monitoring cycle, the control system is plugged into a power source, normally a 120 volt AC source, that provides energy to a closed primary circuit including the microswitch and a plurality of appliance control relays that are each connectable to a switch or valve (collectively referred to as controllers) that is interposed between an appliance or other powered device in the kitchen area, and its respective source of energy. The primary circuit is also connected to secondary circuits that include audible and visual alarms.
Fires are detected by a fire detection system that includes a tensioned cable positioned above the areas where fires may occur. For example, the cable may be positioned inside a hood that is located over the cooking applicances. The cable includes heat fusable links above each appliance. Such links are known in the relevant art and include means for connecting cable segments to opposite sides of the link, with the link being constructed of a material that melts at relatively low temperatures.
When exposed to a cooking fire, the link melts to separate the cable. The cable is attached to a moveable member, preferably a pivotal member that has a pivot end and a distal end. The pivotal member is held at a restrained position when the cable is under tension, and moves to a released position when the cable is released.
The fire extinguishing system also includes a source of fire extinguishing chemicals, e.g., a pressurized tank, and conduits or a piping network leading from the fire extinguishing chemical source to discharge nozzles positioned above the cooking appliances. A normally closed control valve is positioned between the chemical source and the nozzles, preventing discharge of chemicals. This valve is positioned in the path of, and engaged by, the moveable member when the movable member is in the released position.
The microswitch in the control circuit is also positioned in the path of the moveable member, and is also engaged by the moveable member in the released position. Thus, when the moveable member is released, the moveable member contacts the fire extinguisher valve, opening the valve to release the extinguishing material. Also, the moveable member contacts the microswitch to open the primary control circuit. As a result, the relays in the primary circuit change state, activating the controller, e.g., opening an electrical switch, or closing a control valve. As a result the supply of energy, e.g., electricity or gas, is terminated.
Another relay in the primary circuit is also in a second circuit with a normally open, audible alarm circuit, and a normally open visual alarm circuit. Opening of the primary circuit causes the relay to change state, closing the alarm circuits to activate the audible and visual alarms, thereby alerting appropriate personnel. The audible alarm can be immediately deactivated by a pushbutton switch or another kind of a switch. However, no provision for opening the visual alarm circuit is provided. Therefore, the visual alarm continues to signal until the primary circuit is restored to its closed state. This restoration cannot occur until the microswitch is again closed, which requires authorized personnel to recharge the fire extinguishing system and restore the cable to its tensioned state.
Accordingly, one aspect of the present invention is to provide an emergency shutdown system to deenergize appliances upon activation of a fire extinguishing system comprising a microswitch moveable between from a closed position to an open position upon activation of the fire extinguishing system. A plurality of relays are in a first circuit with the microswitch, each of the relays being in a second circuit with an applicance controller. The second circuits are closed when the microswitch is in a closed position, and the relays change from a first state to a second state, opening the second circuits when the microswitch is moved to an open position. An audible alarm is in the circuit with the microswitch, the audible alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the audible alarm also being in a circuit with a silencing switch adapted to return the audible alarm to the unenergized state. A visual alarm is also in the circuit with the microswitch, the visual alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the visual alarm being returnable to the unenergized state only when the fire extinguishing system is returned to the recharged and ready state.
Another aspect of the present invention is to provide a fire control system for use with at least one kitchen appliance comprising a fire detection means to activate a fire extinguishing system; a fire extinguishing system activated upon detection of a fire; and a control system. The control system includes a microswitch moveable between from a closed position to an open position upon detection of a fire; a plurality of relays in a first circuit with the microswitch, each of said relays being in a second circuit with an applicance controller; the second circuits being closed when the microswitch is in a closed position. The relays change from a first state to a second state and open the second circuits when the microswitch is moved to an open position. An audible alarm is in a circuit with the microswitch, with the audible alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the audible alarm also being in a circuit with a silencing switch adapted to return the audible alarm to the unenergized state. A visual alarm is also in the circuit with the microswitch, the visual alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the visual alarm being returnable to the unenergized state only when said fire extinguishing system is returned to the recharged and ready state.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment.